The following relates to the optical arts, optical filter arts, spectrographic arts, pricing information distribution arts, and related arts.
Optical interference filters with high spectral selectivity comprise a stack of layers with alternating refractive index values. These filters can be designed to provide pass-band, stop-band, high-pass, low-pass, or notch filter output. The optical layers are typically deposited on a substrate plate that is optically transparent for the design basis spectrum—hence, the filter is sometimes referred to as a filter plate, and is optically uniform over the area of the plate.
On the other hand, an optical interference filter with different pass-bands or stop-bands or cutoff wavelengths in different areas of the plate is useful for diverse multi-spectral applications such as spectrometer or spectrum analyzer devices. Because it is difficult to controllably vary the layer thickness across the substrate plate during layer deposition, such a multi-spectral filter is sometimes manufactured as a so-called “butcher block” filter array. To build a butcher block filter array, a set of filter plates with different filter characteristics (e.g. different pass-band or stop-band wavelength and/or bandwidth) are formed by appropriate layer depositions. Each filter plate is designed to be uniform over the area of the plate. The filter plates are then diced to form filter elements in the form of strips which are then bonded together in a desired pattern to form the butcher block filter array. A two-dimensional filter array is manufactured by a similar process except that the filter plates are diced to form filter elements that are then bonded together in a desired two-dimensional array.
Some illustrative multi-spectral filter arrays of the foregoing type are described, for example, in Downing et al., U.S. Pub. No. 2014/0307309 A1 published Oct. 16, 2014, which is incorporated herein by reference in its entirety.
Some improvements are disclosed herein.